RU1807428C - Method of protection of meteor radar against interference of oblique incidence-backscatter sounding - Google Patents

Abstract

Usage:. In meteor radar. The essence of the proposal: by making a change in the carrier frequency with a period of 2 D ™ Tc NTn and ------, which allows us to increase the efficiency of suppressing the marking of ROS of inclined-tilt sensing, 2 il

Description

The invention relates to meteor radar and can be used in meteor astronomy, radio communications, synchronization of time scales and when measuring wind parameters of the atmosphere using meteor radars.

The purpose of the invention is to increase the efficiency of protection of the meteor radar from interfering signals of the airborne detection signal while maintaining the repetition rate of probing radio pulses.

The application of the claimed method allows to obtain continuous series of registration of meteoric ionization at any naturally occurring distribution of SCW signals over a range. Protection against VNZ interference becomes especially relevant in the years of maximum solar activity, when daytime recording of meteor traces is impossible for months without an interference suppression device.

The goal is achieved in that in order to separate the meteor signals from the VIZ signals by the difference in the delay of the reflected radio pulses relative to the probing one, the carrier frequency of the probe signal (wobble of the carrier frequency) is periodically changed by an amount exceeding its spectrum width Д f and the bandwidth transmitting the receiver, for which a sequence of rectangular radio pulses with a period Tn and with a carrier frequency that varies discretely from pulse to pulse is emitted. The full radiation cycle Tc consists of N pulses with different carrier frequencies, and the value of Tc is selected from the condition of non-superposition of the signals from the VNZ and meteor radio echo:

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Tu ntn

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(1)

After emitting a radio pulse with number n and a carrier frequency fn, the reflected meteor radio echoes are received for a period of time Tn at the same frequency fn, and before the radiation of the n + 1th radio pulse, the transmitter and receiver are tuned to the frequency

fn + 1-fn + lAf, (2) where 1 0, 1,2 .., N 1,0,1 ....

As a result, the VNZ signals generated by the nth radio pulse and having a significantly longer time delay relative to the probing radio pulse than the meteor radio echo are suppressed in the frequency-selective circuits of the receiver and therefore arrive at the receiver’s antenna after it is tuned to the frequency fn + i . The radiation cycles Tc follow each other without pauses between them.

The main difference between the proposed method and the prototype is that instead of a wobble of the repetition period of the probe pulses, a carrier frequency wobble is used, which allows not only rejecting reflections not satisfying the uniqueness condition, but also effectively suppressing them.

In FIG. 1, a, b, c shows the reflected signals on the screen of the electron beam indicator of the radar with a horizontal scan in range; Fig. 2 is a functional diagram of a device for the technical implementation of the claimed method.

Figure 1, a shows the range intervals occupied by the meteor radio echo and signals from the airborne detection signal, if T 2Dmax / s. Here, no overlap of these signals occurs, but the frequency of the bursts is very low. The experimental data show that the frequency of the packets in this case should not exceed 40 Hz, which corresponds to the maximum range of the signals of the VNZ: Dmax 3750 km. If you increase the sounding frequency (Fig. 1.6), then the meteor radio echo will be superimposed from the pulse with the number n + 1 and the SCH signals caused by the pulse with the number n. To avoid this, in accordance with the proposed method, we use the dual-frequency mode of operation of the radar (Fig. .1, c). Due to an intermittent change in the carrier frequency of the radar, the VHF signals from the previous p-th pulse will be suppressed at the receiver tuned at this time to receive meteor radio echoes from the p + 1-th pulse. In this case, the carrier frequency of all radio pulses with even numbers is fn, and with odd fn + 1. The two-frequency mode allows to increase the sounding frequency by 2 times without the danger of superimposing overhead signals on meteor signals. Since meteor radars, as a rule, operate with a sending pulse frequency exceeding 200 Hz, it is required to apply the N-frequency mode of operation, where N 5.

The invention is carried out using the device shown in Fig. 2.

It consists of a binary totalizer 1, a digital adder 2, frequency synthesizers 3 and 4, a pulsed radio transmitter 5, superheterodyne

receiver 6, transmitting and receiving antennas A1 and A2.

The device operates as follows.

Pulses fT, which specify the frequency of the radiation of the probe pulses of the transmitter, are supplied to the input of the counter 1 with a conversion factor N equal to the number of different carrier frequencies. The output code of counter I controls the output frequency of the synthesizer

h, which serves as the master oscillator of the transmitter 5, modulated by pulses fT and emitting rectangular radio pulses through the antenna A1. The carrier frequency of the emitted oscillations varies in accordance with relation (2). The radio echoes reflected from the ionized meteor tracks are received by the receiving antenna A2 and fed to receiver b, which is tuned by changing the local oscillator frequency

 + k + l} fn + Af (k + l),

(3)

generated by the frequency synthesizer 4, controlled by the code from the counter 1 after adding to it in the adder 2 the constant k associated with the value of the intermediate frequency of the receiver fnn by the ratio:

35

be

kAf.

The frequency difference between the local oscillator and the signal at the same value of I is always equal to the intermediate frequency frm, at which the main amplification and frequency selection of the signal occurs. After detection, the reflected signals are fed to a recording device. The degree of suppression of VNZ signals in this device depends

on the selectivity of the receiver and the step of the frequency spacing Af, which should exceed the width of the spectrum of the probe radio pulse. Thus, this device receives a time interval

With a meteor radio echo, and with the arrival of each modulating signal ft, it tunes the transmitter and receiver to an adjacent frequency, thereby detaching from the SCH signals coming later than the meteor radio echo.

Claims (1)

Claims  A method of protecting a meteor radar from interference from a tilt-and-tearing sounding. none (VNZ), which consists in the fact that they conduct meteor soundings ionized traces by a sequence of radio pulses with a varying carrier frequency from pulse to pulse and the reception of radio pulses reflected from objects located at O-Dmax ranges, characterized in that, in order to increase the suppression efficiency of VIZ interference while maintaining the repetition period of probe pulses, changing the frequency the carrier is produced with a period Tc equal to t mt - L-Viax TC NTn ----- where N is the number of pulses with different carriers for the period TC. Tp is the repetition period of the emitted pulses at one frequency; Dmax - range to the most distant objects causing interference VIZ; c is the speed of light. 7 T / groin met ars or / l-S0 Ј 1000 Fig. / 2000ъООО VIZ or -h L + / L / U .. IS $ h